While major-league baseball players earn millions of dollars and club owners share billions in revenues, minor-leaguers are paid $3,000 to $7,500 per season and train for weeks without pay, in violation of minimum wage and labor laws, their attorneys charge in a lawsuit.

The suit filed against Major League Baseball and three teams, including the San Francisco Giants, said baseball executives and club owners "have preyed upon minor leaguers, who are powerless to combat the collusive power of the MLB cartel."

The major leagues and their teams "have exploited minor leaguers by paying salaries below minimum wage, by not paying overtime wages, and by often paying no wages, at all," said the suit, which was filed this month in U.S. District Court in San Francisco on behalf of three former minor-league players. It seeks class-action status on behalf of thousands of current and former minor-leaguers, dating back at least three years, and damages and civil penalties against MLB and its franchises.

The 6,000 current minor-leaguers have no union or bargaining power and are paid on a fixed scale, set by Major League Baseball, that starts at $1,100 a month at rookie Class A leagues and rises to $2,150 for the top-level Triple-A leagues, the suit said. It said salaries average $3,000 to $7,500 for playing seasons of three to five months.

Players chosen in the amateur draft held each June also receive a one-time signing bonus, "usually around $2,500," the suit said. It said Commissioner Bud Selig, whose office approves all minor-league contracts, placed new limits on those bonuses in 2012.

With games scheduled six or seven days a week, minor-leaguers work at least 50 hours each week, counting workouts and travel time, the suit said. They are not paid anything extra for spring training, offseason instructional leagues, or the year-round conditioning work that teams require, their lawyers said.

Since 1976, when major-league players gained free-agency rights, the suit said, their salaries have increased by more than 2,000 percent, while minor-league pay has risen only 75 percent, less than one-fifth the inflation rate. Revenue for MLB and its 30 teams totaled $7.5 billion in 2012, the suit said.

The other plaintiffs are Aaron Senne, a first baseman and outfielder who spent four years in the Miami Marlins farm system, and Michael Liberto, a third baseman who played three years for Kansas City Royals minor-league clubs.